Saturn is renowned for the colossal hexagon that crowns its northern pole. However, recent scientific investigations have revealed that a comparable atmospheric phenomenon is also present above the planet’s southern pole. In this case, it is a decagon, and it required decades of research for scientists to identify it.
The formation of atmospheric structure
Recent observations with NASA’s Hubble Space Telescope have revealed a giant, evolving, 10-sided atmospheric wave encircling Saturn’s south pole. According to the website phys.org, this discovery represented the first observation of a large, equilateral jet pattern in the southern hemisphere of the planet.
The feature appears remarkably similar to Saturn’s famous hexagon at its north pole but is also distinctly different, suggesting scientists may be witnessing a new atmospheric phenomenon developing on the iconic gas giant.
By piecing together several years of Hubble observations dating to 2023, researchers found subtle hints of the structure beginning to emerge before it became a clearly defined pattern. Those observations were taken as part of Hubble’s Outer Planet Atmospheres Legacy (OPAL) program, which has photographed the outer planets annually for more than a decade.
Scientists have reported unprecedented observations of a phenomenon in Saturn’s southern hemisphere. While the northern hexagon has persisted for the past four decades, this particular feature is distinguished by its ongoing intensification, providing astronomers with a rare opportunity to monitor the evolution of a large-scale atmospheric structure.
The origin of the pattern
The discovery was possible because Saturn’s changing seasons gradually brought the planet’s south pole back into view from Earth, where astronomers who collectively analyze images of Saturn from ground-based observatories first identified it.
Agustín Sánchez-Lavega, lead author of the new study, is a researcher at the University of the Basque Country in Spain. The university manages a website called Planetary Virtual Observatory Laboratory that accepts ground-based images of solar system planets contributed by observers around the world. It was in those images, first in 2024, that Sánchez-Lavega and amateur astronomers Trevor Barry and Jean-Paul Oger noticed a subtle undulating band along the south pole. Additional 2025 imagery taken from the ground hinted more strongly at this decagon structure.
That’s when the Hubble observations came into play. Hubble’s view from space offers unmatched image sharpness and spatial resolution over full rotations of Saturn, without smearing by Earth’s atmosphere.
A wave that traverses multiple layers of the atmosphere
The wave sits within one of Saturn’s powerful jet streams and extends through multiple layers of the atmosphere, indicating it is not just a cloud-level feature but a vertically extended atmospheric structure. The decagon’s apparent position shifts slightly because Hubble captures images at different wavelengths. Those different wavelengths probe different altitudes in Saturn’s atmosphere.
What primarily interests scientists is why this structure has suddenly appeared at this juncture, especially given that similar formations have not been observed previously.
The authors indicate that in order to attain a more comprehensive understanding of the formation process of the decagon, its potential longevity, and its comparison with the enduring hexagon in the northern region, additional research is required. This research should employ the Hubble Space Telescope, NASA’s James Webb Space Telescope, and the analysis of computer models.
Years of observation are yielding beneficial results
Hubble’s long operational lifespan has allowed astronomers to track changes over time in solar system planets and other astronomical objects.
Rather than providing a single snapshot, the OPAL program allows scientists to follow seasonal changes, track short-lived storms and identify other atmospheric features that evolve slowly over time.
“When we started the OPAL program, we expected compelling surprises, but we didn’t know what to expect specifically,” said Mike Wong, a study co-author at the University of California, Berkeley. “A lot of the discoveries we see coming from OPAL are not just based on one observation, but on years and years of data. Regular observations over time are enabling a lot of new findings.”
The team plans to continue observing Saturn to determine whether the decagon settles into a long-lived, stable configuration like the northern hexagon or continues to evolve. Future observations also could help scientists determine what drives the wave, what it reveals about the atmospheric dynamics of giant planets throughout the solar system and how they may relate to those we see here on Earth.
